PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

112 Chapter 4 String Manipulation and Regular Expressions
The %s in the format string is called a conversion specification.This one means “replace
with a string.” In this case, it is replaced with $total interpreted as a string. If the value
stored in $total was 12.4, both of these approaches would print it as 12.4.
The advantage of printf() is that you can use a more useful conversion specification
to specify that $total is actually a floating-point number and that it should have two
decimal places after the decimal point, as follows:
printf (“Total amount of order is %.2f”, $total);
Given this formatting, and 12.4 stored in $total, this statement will print as 12.40.
You can have multiple conversion specifications in the format string. If you have n
conversion specifications, you will usually have n arguments after the format string. Each
conversion specification will be replaced by a reformatted argument in the order they are
listed. For example,
printf (“Total amount of order is %.2f (with shipping %.2f) “,
$total, $total_shipping);
Here, the first conversion specification uses the variable $total, and the second uses the
variable $total_shipping.
Each conversion specification follows the same format, which is
%[‘padding_character][-][width][.precision]type
All conversion specifications start with a % symbol. If you actually want to print a %
symbol, you need to use %%.
The padding_character is optional. It is used to pad your variable to the width you
have specified. An example would be to add leading zeros to a number like a counter.
The default padding character is a space. If you are specifying a space or zero, you do not
need to prefix it with the apostrophe (‘). For any other padding character, you need to
prefix it with an apostrophe.
The - symbol is optional. It specifies that the data in the field will be left-justified
rather than right-justified, which is the default.
The width specifier tells printf() how much room (in characters) to leave for the
variable to be substituted in here.
The precision specifier should begin with a decimal point. It should contain the
number of places after the decimal point you would like displayed.
The final part of the specification is a type code. A summary of these codes is shown
in Table 4.1.
Table 4.1
Type
b
c
d
f
o
Conversion Specification Type Codes
Meaning
Interpret as an integer and print as a binary number.
Interpret as an integer and print as a character.
Interpret as an integer and print as a decimal number.
Interpret as a double and print as a floating-point number.
Interpret as an integer and print as an octal number.